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1、PLCdevelopment1、PLCoverviewProgrammablecontrolleristhefirstinthelate1960sintheUnitedStates,thencalledPicprogrammablelogiccontroller(ProgrammableLogicController)isusedtoreplacerelays.Fortheimplementationofthelogicaljudgment,timing,sequencenumber,andother
2、controlfunctions.TheconceptispresentedPicGeneralMotorsCorporation.Picandthebasicdesignisthecomputerfunctionalimprovements,flexible,genericandotheradvantagesandrelaycontrolsystemsimpleandeasytooperate,suchastheadvantagesofcheappricescombinedcontrollerhar
3、dwareisstandardandoverall.Accordingtothepracticalapplicationoftargetsoftwareinordertocontrolthecontentoftheuserproceduresmemorycontroller,thecontrollerandconnectingtheaccusedconvenienttarget.Tnthemid-1970s,thePichasbeenwidelyusedasacentralprocessingunit
4、microprocessor,importexportmoduleandtheexternalcircuitsareused,large-scaleintegratedcircuitsevenwhenthePicisnolongertheonlylogical(IC)judgmentfunctionsalsohavedataprocessing,PIDconditioninganddatacommunicationsfunctions.InternationalElectrotechnicalComm
5、ission(IEC)standardspromulgatedprogrammablecontrollerforprogrammablecontrollerdraftmadethefollowingdefinition:programmablecontrollerisadigitalelectroniccomputersoperatingsystem,specificallyforapplicationsintheindustrialdesignenvironment.Itusedprogrammab
6、lememory,usedtoimplementlogicintheirinternalstorageoperations,sequencecontrol,timing,countingandarithmeticoperations,suchasoperatinginstructions,andthroughdigitalandanaloginputandoutput,thecontrolofvarioustypesofmachineryorproductionprocesses.Programmab
7、lecontrollerandrelatedperipherals,andindustrialcontrolsystemseasilylinkedtoformawhole,toexpanditsfunctionaldesign.Programmablecontrollerfortheuser,isnon-contactequipment,theprocedurescanbechangedtochangeproductionprocesses.Theprogrammablecontrollerhasbe
8、comeapowerfultoolforfactoryautomation,widelypopularreplication.Programmablecontrollerisuser-orientedindustriesdedicatedcontrolcomputer,withmanydistinctivefeatures.First,highreliability,anti-interferencecapability;Second,programmi
